Combinational Intercalation-Conversion-Intercalation reaction of CuInS@PPy anode for Sodium-Ion batteries.

Polypyrrole-coated CuInS (CuInS@PPy) composite was prepared through the chemical vapor transport method and subsequent in situ polymerized coating strategy. In this unique nanoarchitecture, the PPy coating layer plays a crucial role in improving the conductivity of the composite, suppressing the volume change of CuInS, and maintaining the structural integrity of electrode material upon cycling. In addition, the electrochemical reaction mechanism and kinetics of CuInS@PPy were investigated in-depth. Benefitting from the synergism of its combinational intercalation-conversion-intercalation reaction mechanism and the high conductivity of the PPy coating layer, CuInS@PPy electrode exhibits superior rate capability and cycling stability for sodium-ion batteries, with a capacity of 404.8 mA h g at 4 A g over 2500 cycles.